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Asterisms

This is a page about those star patterns that are (mostly) not constellation lines, but none the less noteworthy. Therefore asterisms. They are for the most made up solely based upon their recognizability, and because of this are a great help to orient oneself in the night sky.

I selected star patterns with sufficient brightness and size to be visible to the naked eye, at least in optimal conditions with clear weather and a very dark sky. To simulate light pollution you can limit the minimum brightness of visible stars with the slider below the map. For the relations between them I've included guiding lines that follow linear alignments between bright stars. The asterisms are classified 1...5 by the approximate average magnitude of their member stars.

With the location and date-time controls it is possible to display the hemisphere for a given point on Earth at any time not too distant from the present. With the "Here" and "Now" buttons it is possible to select the current local time of your device, which is set as default on loading, and the current location, if your device supports that. It may be necessary to give explicit permission to do so if asked. Otherwise put in valid coordinates in the latitude (first field) and longitude boxes. A click on the date-time field displays the date & time-picker, that also allows to set the time zone. Note that it is currently possible to choose incompatible values for time zone and location, which results in nonsensical display, so try to avoid that.

Some of the asterisms are constellations (Cassiopeia, Crux, Scorpius), some are parts of constellations (Big Dipper, Sickle, Teapot, Orion's Belt and Sword ...) and some are traditionally known patterns of bright stars grouped into simple shapes (Pegasus Square, Summer Triangle, Great Diamond, Winter Hexagon), that involve the brightest stars from many different constellations that happen to be visible in the evening sky in each (northern) season. And Argo Navis is an old constellation that was dismantled into the smaller pieces Carina, Vela, Puppis and Pyxis because it was deemed just too big. But for an asterism it is just fine. At least I hope, because I don't have much experience with the southern sky, I'm not sure if it makes an easy to recognize pattern. I'm willing to stand corrected on this one.

I think the grouping of simple patterns along the celestial equator is interesting, for they align easily with the seasons (from a northern perspective): The Summer Triangle and Winter Hexagon are even named after the seasons in which they are best visible. The Great Diamond is up in the spring and the Pegasus Square is best visible in the fall, completing the year. This way it is possible to draw a text-diagram of the entire night sky with most the brightest asterisms (from the northern hemisphere):

'W' Dipper
Square Triangle Diamond Hexagon
Teapot Cross Boat

That might even make a useful mnemonic.

Along with the asterisms I included some useful alignments: The Southern Pointer (Alpha and Beta Centauri) points to the Southern Cross, which in turn points to the celestial South Pole, and the two hindmost stars of the Big Dipper point to the celestial North Pole. Then there is the alignment of Orion's Belt with Sirius, that I'm calling "The Leash" here, since Canis Major is supposed to be Orion's hunting dog, along with Canis Minor. The other dashed guiding lines show linear relations of bright star and are useful for finding the way between bright asterisms.

Below is a table of all the member stars of the featured asterisms, ordered by groups of proximity and/or season. The brightest asterism in each group is listed first, then all hose grouped around it clockwise from the north, for southern groups clockwise from the south. For reference, first here's a chart with all the brightest asterisms and their lookalikes:

"The Leash" Canis Major Alpha CMa Sirius 06:45:08.9 -16:42:58 -1.46 A1Vm
Orions Belt points toward Sirius. This is my own invention and refers to the fact that it points from Orion
to the neck (i.e. Alpha CMa) of his larger dog.